Bromine-containing 1,2-bis(phenyl)difluoromethanes and method of imparting flame retardancy to flammable materials

ABSTRACT

Bromine containing 1,2-bis(phenyl)difluoromethane derivatives, a method for their preparation and their use in flame retardant compositions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Provisional PatentApplication No. 60/103,335 filed Oct. 7, 1998.

FIELD OF THE INVENTION

The present invention relates to bromine-containing1,2-bis(phenyl)difluoromethanes of the formula:

wherein x=1-5, and y=0-5. Also disclosed is a method for the preparationof these compounds. The compounds of formula I are useful asintermediates in producing compounds exhibiting pharmaceutical oragricultural activity, and the compounds of formula I are useful asflame retardants.

BACKGROUND OF THE INVENTION

Decabromodiphenyl alkanes (C₁₋₁₀), such as decabromodiphenyl methane anddecabromodiphenyl ethane are known compounds that are useful as flameretardants, as disclosed in Hussain U.S. Pat. No. 5,008,477. Thecompounds are prepared by brominating diphenyl alkane, in the presenceof a bromination catalyst such as AlCl₃ and/or AlBr₃, at a temperatureof about 50° C. to about 60° C., wherein the alkane group has 1-10carbon atoms. It has been found, in accordance with the presentinvention, that the above-defined bromine-containing1,2-bis(phenyl)difluoromethylene compounds can be prepared and exhibitimproved flame retardancy to flammable materials.

SUMMARY OF THE INVENTION

The novel compounds in accordance with the present invention have thegeneral formula

where:

x is equal to 1-5, y is equal to 0-5; and x=1, y=1 (for o,o′; o,m′;o,p′; m,m′; and m,p′ only). In the case of x=1 and y=0, the paracompound is known, but is novel as a flame retardant. Similarly, forx=1, y=1, the para, para′ compound is known, but is novel as a flameretardant.

The compounds of formula I can be used as synthesis intermediates forthe preparation of agricultural and pharmaceutical compounds, and canalso be used as flame retardants.

DETAILED DESCRIPTION OF THE INVENTION

The novel compounds in accordance with the present invention have thegeneral formula:

where:

x is equal to 1-5, and y is equal to 0-5; and where x=1, and y=0, o andm only (excluding para bromo); and where x=1, and y=1, o,o′; o,m′; o,p′;m,m′; and m,p′ (excluding para, para′), the excluded compounds are knownin the art per se, but not as flame retardants).

The novel compounds are any of the following compounds:

The compounds of formula I may be prepared in a number of ways. Forexample, the compounds may be prepared via the reaction of1,2-bis(phenyl)difluoromethane with a bromination agent, such aselemental bromine in fuming sulfuric acid:

wherein x=1-5; and y=0-5.

The amount of bromine reacted with the 1,2-bis(phenyl)difluoromethanereactant is readily controlled by adjusting the molar ratio of bromineto 1,2-bis(phenyl)difluoromethane. Excess bromine favors the formationof the more highly brominated compounds of the present invention,whereas lower amounts of bromine favor the production of the lessheavily brominated compounds of the present invention.

Alternatively, as is taught in the prior art, different brominationagents may be employed, for example, elemental bromine in the presenceof a Lewis acid, or N-bromo compounds such as N-bromosuccinimide anddibromodimethylhydantoin.

The 1,2-bis(phenyl)difluoromethane precursor may be prepared via thereaction of benzophenone with a fluorination agent, such as SF₄,diethylaminosulfur trifluoride (DAST), alkylsulfur trifluorides orarylsulfur trifluorides. Alternatively, benzophenone can be transformedto the corresponding hydrazone or 1,3-dithiolane followed by treatmentwith a fluorination agent such as hydrogen fluoride (HF),polyvinylpyridinium poly(hydrogen fluoride) [PVPPHF], pyridiniumpoly(hydrogen fluoride) [PPHF], and an N-bromo compound, such asN-bromosuccinimide or dibromdimethyl hydantoin. Preferred is PVPPHF orPPHF and an N-bromo compound, such as N-bromosuccinimide ordibromdimethyl hydantoin.

All of the above-mentioned compounds are useful as flame retardants foruse with any flammable material, as well as the following compounds:

where

x=0 or 1 and y=0 or 1 and x+y=1-2.

When used as a flame retardant for a flammable material, thebromine-containing 1,2-bis(phenyl)difluoromethane should be incorporatedinto or onto the flammable material in an amount sufficient to obtainthe desired flame retardancy, which varies with the particular flammablematerial in which the compound(s) is incorporated. In general, theamount of compound(s) incorporated into the flammable material is in therange of about 2% to about 50% by weight of flammable material,preferably about 5% to about 30%, based on the weight of flammablematerial.

The bromine-containing 1,2-bis(phenyl)difluoromethanes of the presentinvention are useful for flame retardation of any flammable material,including monomers and oligomers, but are particularly advantageous forflame retarding thermoplastic and thermosetting polymers and copolymers.Examples include polyolefins, polyurethanes, polyamides, polyimides,polycarbonates, polyethers, polyesters, epoxy resins, polyphenols, andelastomers, such as natural rubber, butyl rubber, and polysilanes. Theoligomers and polymers may be cross-linked or non cross-linked and maycontain typical additives, such as plasticizers, stabilizers,antioxidants, fillers, pigments and the like. The flame retardantcompounds of the present invention can be compounded into the flammablematerial at any stage of processing, e.g., added to the monomer oroligomer prior to, during, or after polymerization, or during extrusion,melt blending, or molding of the flammable material, e.g., polymer.

The following examples are provided for illustrative purposes only andshould not be construed to limit the scope of the invention.

EXAMPLE 1 Preparation of 1,2-bis(phenyl)difluoromethane

To a polyethylene bottle containing a suspension of N-bromosuccinimide(1.2 g, 6.6 mmol) and polyvinylpyridinium poly(hydrogen fluoride) [1.9g, 59% w/w HF] in dry methylene chloride (10 mL) maintained at −40° C.was added dropwise a solution of benzophenone hydrazone (0.52 g, 2.6mmol) in methylene chloride (5 mL). The mixture was stirred and allowedto warm to room temperature over the course of 30 minutes and thenstirred at room temperature for 2 hours. The mixture was then filteredand the wet cake washed with sodium bicarbonate solution and water, thendried over magnesium sulfate and filtered. The methylene chloride wasremoved under reduced pressure and the residue was redissolved inpentane which gave a precipitate that was removed by filtration. Thefiltrate was concentrated to yield 0.4 g of crude1,2-bis(phenyl)difluoromethane. The crude product was purified viacolumn chromatography to yield 0.30 g of a clear oil, shown to be thedesired product by nuclear magnetic resonance NMR), Fourier TransformInfra Red (FTIR) and gas chromatography/mass spectrometry (GC/MS)analysis.

EXAMPLE 2 Preparation of 1,2-bis(pentabromophenyl)difluoromethane

To a flask charged with 1,2-bis(phenyl)difluoromethane (1.0 g, 5.00mmol), which is as described in Example 1, is added 34.7 g of 65% fumingsulfuric acid. Bromine (7.87 g, 49.5 mmol) is then added dropwise over aperiod of 30 minutes. The solution is then stirred for 4.5 hours at roomtemperature, and the reaction mixture is poured onto ice and theresulting mixture is then filtered. The recovered solid is washed withseveral portions of water and methylene chloride and can be identifiedby nuclear magnetic resonance (NMR), mass spectrometry (MS), FourierTransform infra Red (FTIR), and bromine content analysis as1,2-bis(pentabromo-phenyl)difluoromethane.

EXAMPLE 3

Employing the method of Example 2, but with lower bromine to1,2-bis(phenyl)difluoromethiane molar ratios (0.5-9 to 1) products ofthe current invention containing from 3 to 9 bromine atoms are readilyprepared.

What is claimed is:
 1. Bromine-containing1,2-bis(phenyl)difluoromethanes of the formula:

where x=1-5, and y=0-5; and wherein x=1 and y=0, ortho and meta only;and wherein x=1 and y=1, ortho, ortho′; ortho, meta′; ortho, para′;meta, meta′; and meta, para′.
 2. A bromine-containing1,2-bis(phenyl)difluoromethane according to claim 1, having a formulaselected from the group consisting of


3. A bromine-containing 1,2-bis(phenyl)difluoromethane according toclaim 1, having the formula:


4. A bromineontaining 1,2-bis(phenyl)difluoromethane according to claim1, of the formula

wherein x=2-5 and y=2-5.
 5. A method of providing flame retardancy to aflammable material comprising incorporating into said flammable materiala flame retardant-effective amount of a bromine-containing1,2-bis(phenyl)difluoromethane of the formula:

wherein x=1-5, and y=0-5.
 6. A method in accordance with claim 5,wherein the flammable material comprises a polymer.
 7. A method inaccordance with claim 6, wherein the polymer is a polymer or copolymerselected from the group consisting of polyolefins, polyurethanes,polyamides, polyimides, polycarbonates, polyethers, epoxy resins,polyphenols, elastomers, polysiloxanes, and mixtures thereof.
 8. Amethod in accordance with claim 5, wherein the bromine-containing1,2-bis(phenyl)difluoromethane is incorporated into the flammablematerial in an amount in the range of about 2% to about 50% by weight,based on the weight of the flammable material.
 9. A method in accordancewith claim 5, wherein the bromine-containing1,2-bis(phenyl)difluoromethane is incorporated into the flammablematerial in an amount in the range of about 5% to about 30% by weight,based on the weight of the flammable material.
 10. A method of making abrominecontaining 1,2-bis(phenyl)difluoromethane of the formula:

wherein x=1-5 and y=0-5; wherein x=1 and y=0, ortho and meta only; andwherein x=1 and y=1, ortho, ortho′; ortho, meta′; ortho, para′; meta,meta′; and meta, para′, comprising brominating1,2-bis(phenyl)difluoromethane by reaction of the1,2-bis(phenyl)difluoromethane with a bromination agent.
 11. A method inaccordance with claim 10, wherein the 1,2-bis(phenyl)difluoromethane isbrominated with a bromination agent selected from the group consistingof elemental bromine, N-bromosuccinimide, dibromodimethylhydantoin, andmixtures thereof.
 12. A method in accordance with claim 11, wherein thebromination agent is elemental bromine.
 13. A method in accordance withclaim 12, wherein the bromine is combined with a Lewis acid for contactand reaction with the 1,2-bis(phenyl)difluoromethane.
 14. A method inaccordance with claim 10, further including the step of forming1,2-bis(phenyl)difluoromethane by fluorinating benzophenone with afluorination agent.
 15. A method in accordance with claim 14, whereinthe fluorination agent is selected from the group consisting of SF₄,diethylaminosulfur trifluoride, and mixtures thereof.
 16. A method inaccordance with claim 10, wherein the bromination agent is added to the1,2-bis(phenyl)difluoromethane in a molar ratio in the range of 1 to 20moles of bromination agent per mole of 1,2-bis(phenyl)difluoromethane.17. A method in accordance with claim 16, wherein the1,2-bis(phenyl)difluoromethane is formed by contacting benzophenone with0.2 to 2 moles of fluorination agent per mole of benzophenone.
 18. Amethod in accordance with claim 17, wherein the fluorination agent isdiethylaminosulfar trifluoride.
 19. A method in accordance with claim18, wherein the diethylaminosulfur trifluoride is dissolved in anorganic solvent.
 20. A method in accordance with claim 19, wherein theorganic solvent is carbon tetrachloride.
 21. A method in accordance withclaim 10, further including the step of forming1,2-bis(phenyl)difluoromethane by first transforming benzophenone to acompound selected from the group consisting of the correspondinghydrazone or 1,3-dithiolane followed by treatment of the hydrazone or1,3-dithiolane with a fluorinating agent and an N-bromo compound.
 22. Amethod in accordance with claim 21, wherein the benzophenone istransformed to the 1,2-bis(phenyl)difluoromethane by reaction withhydrazine.
 23. A method in accordance with claim 21, wherein thebenzophenone is transformed to the 1,2-bisnphenyl)difluoromethane byreaction with 1,2-ethanedithiol.
 24. A method in accordance with claim21, wherein the fluorinating agent is selected from the group consistingof hydrogen fluoride, polypyridinium poly(hydrogen fluoride),polyvinylpyridinium poly(hydrogen fluoride), and mixtures thereof.
 25. Amethod in accordance with claim 21, wherein the N-bromo compound isselected from the group consisting of N-bromosuccminide,dibromodimethylhydantoin, and mixtures thereof.